Results from a Test-to-Release from Isolation Strategy Among Fully Vaccinated National Football League Players and Staff Members with COVID-19 ...
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Morbidity and Mortality Weekly Report
Results from a Test-to-Release from Isolation Strategy Among Fully Vaccinated
National Football League Players and Staff Members with COVID-19 —
United States, December 14–19, 2021
Christina D. Mack, PhD1; Erin B. Wasserman, PhD1; Marie E. Killerby, VetMB2; Rieza H. Soelaeman, PhD2; Aron J. Hall, DVM2;
Adam MacNeil, PhD2; Deverick J. Anderson, MD3; Patti Walton, MHSA4; Saamir Pasha, MPH1; Emily Myers5; Catherine S. O’Neal, MD6;
Christopher J. Hostler MD3; Navdeep Singh, MD7; Thom Mayer, MD8, Allen Sills, MD5
During December 2021, the United States experienced a COVID-19 should continue taking precautions, including cor-
surge in COVID-19 cases, coinciding with predominance of rect and consistent mask use, for a full 10 days after symptom
the SARS-CoV-2 B.1.1.529 (Omicron) variant (1). During this onset or initial positive test result if they are asymptomatic.
surge, the National Football League (NFL) and NFL Players The NFL consists of 32 member clubs based in 24 states.
Association (NFLPA) adjusted their protocols for test-to-release NFL required COVID-19 vaccination (as of June 7, 2021)
from COVID-19 isolation on December 16, 2021, based on and boosters (as of December 27) for staff members who
analytic assessments of their 2021 test-to-release data. Fully directly interact with players and incentivized but did not
vaccinated* persons with COVID-19 were permitted to return require vaccination among players. By October 13, 2021, the
to work once they were asymptomatic or fever-free and experi- NFL population vaccination rate was >96% (staff members
encing improving symptoms for ≥24 hours, and after two nega- >99%; players >94%) (5). For most of the 2021 season, fully
tive or high cycle-threshold (Ct) results (Ct≥35) from either of vaccinated persons were tested weekly and unvaccinated per-
two reverse transcription–polymerase chain reaction (RT-PCR) sons were tested daily by RT-PCR; antigen testing was not
tests† (2). This report describes data from NFL’s SARS-CoV-2 used. On December 18, 2021, testing protocols transitioned
testing program (3) and time to first negative or Ct≥35 result to symptom- or exposure-based testing, determined through
based on serial COVID-19 patient testing during isolation. enhanced symptom screening and contact tracing for fully
Among this occupational cohort of 173 fully vaccinated adults vaccinated persons, resulting in approximately two thirds the
with confirmed COVID-19 during December 14–19, 2021, number of tests, but retaining a high level of case detection
a period of Omicron variant predominance, 46% received (6). Around the same time, NFL also updated test-to-release
negative test results or had a subsequent RT-PCR test result protocols (Box). Daily testing was requested for all fully vac-
with a Ct≥35 by day 6 postdiagnosis (i.e., concluding 5 days cinated persons with COVID-19, who could be released from
of isolation) and 84% before day 10. The proportion of isolation if they were asymptomatic or fever-free with symp-
persons with positive test results decreased with time, with toms improved for 24 hours with medical staff clearance, and
approximately one half receiving positive RT-PCR test results receipt of two negative or Ct≥35 RT-PCR test results (point of
after postdiagnosis day 5. Although this test result does not care [POC] or laboratory-based) within 24 hours (2). Although
necessarily mean these persons are infectious (RT-PCR tests Ct values have not been validated as a measure of infectious-
might continue to return positive results long after an initial ness (7), a conservative Ct cutoff was chosen by NFL based
positive result) (4), these findings indicate that persons with on higher Ct values correlating with limited culturable virus
in other studies (8).
* Fully vaccinated was defined as ≥14 days after primary vaccination series
COVID-19 cases § identified during December 12,
completion, with or without a booster. Partially vaccinated was defined by NFL 2021–January 1, 2022, were stratified by whether persons
as receipt of 1 dose of a 2-dose series or 40. Use of this assay with alternative Ct cutoffs is RT-PCR tests alongside clinical adjudication. For COVID-19 cases, day of
not authorized by FDA. The Mesa Biotech Accula test produces a qualitative diagnosis (“day zero”) was defined as the day of first positive test result, which
result (positive/negative) without Ct values. in this setting of high access to testing was often the day of symptom onset.
US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / February 25, 2022 / Vol. 71 / No. 8 299Morbidity and Mortality Weekly Report
BOX. Test-to-release from isolation procedures — National Football League, United States, June 16, 2021–January 1, 2022
June 16, 2021 (NFL season start)
• Requested daily laboratory-based and POC RT-PCR testing* for all fully vaccinated† persons with COVID-19
• Permitted fully vaccinated persons with COVID-19 to voluntarily return to work early (before 10 days since first
positive test) upon meeting the following testing and clinical criteria:
• Testing criteria
ű Two negative laboratory-based RT-PCR tests separated by ≥24 hours
ű One negative POC RT-PCR test before entry on the date of entry
• Clinical criteria
ű Asymptomatic for 48 hours
ű Medical clearance by the team physician
ű Review of test results by the NFL Chief Medical Officer and clinical consultants
• Upon return, all persons followed existing NFL-NFLPA masking and behavioral protocols
November 9, 2021
• Requested daily laboratory-based RT-PCR testing for all fully vaccinated persons with COVID-19
• Permitted fully vaccinated persons with COVID-19 to voluntarily return to work early (before 10 days since first
positive test) upon meeting the following testing and clinical criteria
• Testing criteria
ű Days 1–6 after a confirmed positive test result: two negative laboratory-based RT-PCR test results separated by ≥24 hours
ű Days 7–10 after a confirmed positive test result: 1) one negative laboratory-based RT-PCR test result; and 2) one
negative POC RT-PCR test result before entry on the day following specimen collection of initial laboratory-based
RT-PCR test (taken ≥24 hours later)
• Clinical criteria: Days 1–6 or Days 7–10
ű Asymptomatic for 48 hours (other than loss of taste or smell)
ű Medical clearance by the team physician
ű Confirmation of test results by the NFL Chief Medical Officer and clinical consultants
• Upon return, all persons followed existing NFL-NFLPA masking and behavioral protocols
See box footnotes on the next page.
previous high performance in this setting (3) (NFL, unpub- tested ≥6 times during infection, with a final test on day 8 or 9
lished data). Sequence analysis was performed using Illumina postdiagnosis or achieved two negative or Ct≥35 RT-PCR
COVIDSeq (9) for a portion of cases. Symptoms throughout test results (after which testing ceased). Subsequent transmis-
illness were clinically monitored but not centrally recorded; sion from persons returning from isolation early could not be
NFL clubs requesting early return permission were required ascertained because of high community COVID-19 incidence
to provide documentation of asymptomatic or improving and limited Omicron genomic sequencing diversity. The
symptom status. Clubs were requested to closely monitor analysis in this report was conducted by IQVIA on behalf of
persons returning and report any new symptoms; persons NFL with CDC’s support. This activity was reviewed by CDC
returning were required to adhere to applicable NFL-NFLPA and was conducted consistent with applicable federal law and
masking policies. CDC policy.¶
This report describes results from the NFL test-to-release During December 12, 2021–January 1, 2022, a surge in
from isolation strategy for fully vaccinated persons with COVID-19 cases occurred among NFL players and staff, with
confirmed COVID-19 during December 14–19, 2021. an average of 336 cases per week, compared with 30 cases per
These dates reflect a period during which the Omicron vari- week during the preceding 3 months. Sixty-six (53%) cases
ant accounted for 97% of sequenced viruses, and protocols occurred among 125 unvaccinated persons, three (23%)
requested COVID-19 patients test daily for 10 days after
diagnosis (isolation ended on day 5 beginning December 28, ¶ 45C.F.R. part 46, 21 C.F.R. part 56; 42 U.S.C. Sect. 241(d); 5 U.S.C. Sect.
2021). Fully vaccinated persons were included if they were 552a; 44 U.S.C. Sect. 3501 et seq.
300 MMWR / February 25, 2022 / Vol. 71 / No. 8 US Department of Health and Human Services/Centers for Disease Control and PreventionMorbidity and Mortality Weekly Report
BOX. (Continued) Test -to-release from isolation procedures — National Football League, United States, June 16, 2021–January 1, 2022
December 16, 2021§
• Strongly requested daily testing using laboratory-based and POC RT-PCR after a confirmed positive test result for all
fully vaccinated persons with COVID-19
• Permitted fully vaccinated persons with COVID-19 to voluntarily return to work early (before 10 days since first
positive test result) upon meeting the following testing and clinical criteria
• Testing criteria: two samples collected ≤24 hours of each other on Day 1 or thereafter (may be collected on the same day;
must be separate swabs)
ű Two negative or Ct≥35 laboratory-based RT-PCR test results; or
ű One negative or Ct≥35 laboratory-based RT-PCR test result and one negative POC RT-PCR test result; or
ű Two negative POC RT-PCR test results
• Clinical criteria
ű Asymptomatic or fever-free and improving symptoms for ≥24 hours
ű Medical clearance by the team physician
ű Confirmation of test results by the NFL Chief Medical Officer and clinical consultants
• Although Ct values are not a measure of infectiousness¶ a Ct cutoff of 35 was chosen based on higher Ct values
correlating with limited culturable virus using alternative RT-PCR tests**
• Upon return, all persons followed existing NFL-NFLPA masking and behavioral protocols
December 28, 2021
• Allowed for day 5 return if fever-free for ≥24 hours, asymptomatic or improving symptoms, and cleared by team
physician, regardless of vaccination status††
• Once cleared from isolation (between Days 5 and 10), all persons were required to wear a KN95 or N95 mask at all
times other than when actively engaged in physical activity at practice or in a game until 10 days following positive test
result, at which time they returned to existing NFL-NFLPA masking protocols
• Fully vaccinated persons with COVID-19 could return before Day 5 by meeting the December 16 protocol criteria.
Upon return, persons were required to follow existing NFL-NFLPA masking and behavioral protocols.
Abbreviations: FDA = Food and Drug Administration; NFL = National Football League; NFLPA = National Football League Players Association; POC = point-
of-care; RT-PCR = reverse transcription–polymerase chain reaction.
* SARS-CoV-2 tests included either laboratory-based real-time RT-PCR (BioReference Laboratories RT-PCR assay [Roche Cobas assay], Roche) or POC RT-PCR
(Mesa Biotech Accula SARS-CoV-2 test, Mesa Biotech Inc.); the Roche Cobas RT-PCR test used received FDA Emergency Use Authorization as a qualitative
diagnostic assay with a Ct cutoff of >40. Use of this assay with alternative Ct cutoffs is not authorized by FDA. The Mesa Biotech Accula test produces only
a qualitative result (positive/negative) and no Ct values.
† Fully vaccinated was defined as ≥14 days after primary vaccine series completion, with or without a booster. Under NFL-NFLPA protocols, persons with 1 dose
of a 2-dose mRNA vaccination series and a documented history of COVID-19 were subject to the same requirements as fully vaccinated persons in the NFL-
NFLPA protocols; however, these persons were excluded from analyses summarizing the test-to-release from isolation strategy.
§ https://www.nfl.com/news/nfl-updates-covid-19-protocols-to-allow-for-quicker-return-from-quarantine-for-v
¶ https://www.cdc.gov/coronavirus/2019-ncov/lab/faqs.html
** https://academic.oup.com/cid/article/73/11/e3884/6018217
†† https://www.cdc.gov/media/releases/2021/s1227-isolation-quarantine-guidance.html
among 13 partially vaccinated persons, and 924 (14%) among Using data from December 14–19, 2021, a total of 218 (5%)
6,443 fully vaccinated persons.** Among 117 (12%) cases cases were identified in NFL players and staff members among
with a sequenced virus isolate during this period, 111 (95%) 4,134 persons tested; 87 (97%) of 90 sequenced isolates were
were classified as Omicron and six (5%) as the SARS-CoV-2 Omicron. Among 201 COVID-19 cases in fully vaccinated
B.1.617.2 (Delta) variant. persons that were either confirmed as Omicron or unsequenced
(presumed Omicron), 173 (86%) tested for isolation release;
** The remaining 15 cases occurred among 75 persons with 1 dose of a 2-dose the remaining 28 (14%) did not test frequently enough for
mRNA vaccination series and a documented history of COVID-19, who were inclusion. Among these 173 persons, 53 (31%) obtained at
subject to the same requirements as fully vaccinated persons in the NFL-
NFLPA protocols. These persons were not included in analyses summarizing least one negative or Ct≥35 RT-PCR test result on or before
the test-to-release from isolation strategy. day 5 postdiagnosis, 79 (46%) on or before day 6 (concluding
5 full days of isolation), and 146 (84%) within 10 days after
US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / February 25, 2022 / Vol. 71 / No. 8 301Morbidity and Mortality Weekly Report
diagnosis. Among the 146 persons with at least one negative
Summary
or Ct≥35 RT-PCR test result in the 10 days after diagnosis,
What is already known about this topic?
the median interval from diagnosis to first negative result was
6 days (IQR = 5–8 days); among all 173 persons, the median On December 16, 2021, the National Football League (NFL)
updated its test-to-release from COVID-19 isolation protocols in
interval was 7 days (IQR = 5–9 days) (Figure 1). response to increasing COVID-19 cases and predominance of
Overall, 130 (75%) of 173 persons tested for return from the SARS-CoV-2 Omicron variant.
isolation met NFL-NFLPA protocol testing criteria before What is added by this report?
10 days, with median interval to second negative or Ct≥35
Among 173 vaccinated adults with COVID-19 undergoing
test result of 7 days (IQR = 5–8 days); 122 (71%) met both serial reverse transcription–polymerase chain reaction
testing and clinical criteria and were eligible to return to work (RT-PCR) testing during Omicron predominance, 46% received
before 10 days after diagnosis (Figure 2). Among the 130 per- a negative or high cycle threshold RT-PCR test result on or
sons who tested for early return from isolation, 116 applied before day 6 postdiagnosis.
for early return; the remaining 14 did not because either their What are the implications for public health practice?
job function did not require early return (six), or they were Although a positive RT-PCR test result does not necessarily
still symptomatic (six); two did not apply for early return for indicate infectiousness, these data indicate that persons with
unknown reasons. Among 173 persons who tested for release COVID-19 should continue to take precautions, including
correct and consistent mask use, for a full 10 days after
from isolation, the median time to return to work was 8 days
symptom onset or after initial positive test result if they
(IQR = 6–10 days). None of the persons who returned to work are asymptomatic.
reported onset of new symptoms after early return during the
10 days after diagnosis.
FIGURE 1. Percentage of 173 fully vaccinated* COVID-19 patients (SARS-CoV-2 B.1.1.529 [Omicron] and unsequenced†) with a negative or
cycle-threshold ≥35§ reverse transcription–polymerase chain reaction test result, by number of days after diagnosis — National Football
League, United States, December 14–19, 2021
100
Percentage with negative or Ct≥35 RT-PCR test result
90
80 46% after
5 full days
70
60
50
40
30
20
10
0
0 1 2 3 4 5 6 7 8 9
No. of days after diagnosis
Abbreviations: Ct = cycle threshold; NFL = National Football League; NFLPA = National Football League Players Association; RT-PCR = reverse transcription–polymerase
chain reaction.
* Fully vaccinated was defined as ≥14 days after primary vaccine series completion. Under NFL-NFLPA protocols, persons with 1 dose of a 2-dose mRNA vaccination
series and a documented history of COVID-19 were subject to the same requirements as fully vaccinated persons in the NFL-NFLPA protocols; however, these persons
were excluded from analyses summarizing the test-to-release from isolation strategy.
† Among 173 cases, 77 (45%) were sequenced as Omicron, and 96 (55%) were not sequenced (unsequenced). During December 14–19, 2021, 87 (97%) of 90 sequenced
isolates from 218 total cases were Omicron, therefore unsequenced cases were presumed Omicron.
§ Although Ct values are not a measure of infectiousness (https://www.cdc.gov/coronavirus/2019-ncov/lab/faqs.html) a Ct cutoff of 35 was chosen by NFL based on
higher Ct values correlating with limited culturable virus using alternative RT-PCR tests (https://academic.oup.com/cid/article/73/11/e3884/6018217).
302 MMWR / February 25, 2022 / Vol. 71 / No. 8 US Department of Health and Human Services/Centers for Disease Control and PreventionMorbidity and Mortality Weekly Report
Discussion isolation, and transmission after early return from isolation
This report describes results from the NFL test-to-release could not be documented, none of the persons who returned
from isolation strategy for fully vaccinated NFL players and to work experienced new symptoms detected by in-facility
staff members with COVID-19 during December 14–19, symptom monitoring.
2021, after emergence of the Omicron variant. Before day 10 CDC recommends an additional 5 days of mask use when
postdiagnosis, ≥71% of infected persons were asymptomatic around others following an isolation period of 5 days, which
or significantly improved for 24 hours and had received two can end when a person has been fever-free for 24 hours and
negative or Ct≥35 test results and were therefore eligible to other symptoms have improved (10). The results from this
return to work under NFL-NFPLA protocols. Although analysis support this masking recommendation, although
persons were not systematically tested after return from infectiousness or transmission could not be assessed. Under
FIGURE 2. Test-to-release from isolation results among 201 fully vaccinated* COVID-19 patients (SARS-CoV-2 B.1.1.529 [Omicron] and
unsequenced†) undergoing serial reverse transcription–polymerase chain reaction testing§ to allow release from isolation — National Football
League, December 14–19, 2021¶,**,††
201 cases among fully vaccinated National Football League players and staff members
Initial positive test results received December 14–19, 2021; confirmed or presumed Omicron
173 (86%)
28 (14%)
Tested approximately daily from initial positive test result until isolation end
Did not test frequently enough
(meeting criteria or 10 days post-diagnosis)
27 (16%) 146 (84%)
No RT-PCR–negative or Ct≥35 test result At least one RT-PCR–negative or Ct≥35 test
during 9-day testing period result within 10 days
130 (89%) 16 (11%)
Met NFL testing criteria for release One RT-PCR–negative or
from isolation (two RT-PCR–negative or Ct≥35 test result
Ct≥35 test results)
Abbreviations: Ct = cycle threshold; NFL = National Football League; NFLPA = National Football League Players Association; POC = point of care; RT-PCR = reverse
transcription–polymerase chain reaction.
* Fully vaccinated was defined as ≥14 days after primary vaccine series completion, with or without a booster. Under NFL-NFLPA protocols, persons with 1 dose of
a 2-dose mRNA vaccination series and a documented history of COVID-19 were subject to the same requirements as fully vaccinated persons in the NFL-NFLPA
protocols; however, these persons were excluded from analyses summarizing the test-to-release from isolation strategy.
† Among 201 cases, 79 (39%) were sequenced as Omicron, and 122 (61%) were not sequenced (unsequenced). During December 14–19, 2021, 87 (97%) of 90
sequenced isolates from 218 total cases were Omicron, therefore unsequenced cases were presumed Omicron.
§ RT-PCR tests included either laboratory-based real-time RT-PCR (Bioreference Labs RT-PCR assay [Roche Cobas assay], Roche) or POC RT-PCR (Mesa Biotech Accula
SARS-CoV-2 Test, Mesa Biotech Inc.).
¶ Among those who did not test frequently enough, 26 (93%) had a job function that did not require regular attendance in facility or immediate return or were
travel-related.
** Among 130 persons who met testing criteria, 122 (94%) met testing and clinical criteria for release from isolation, six had continuing symptoms, and two did not
apply for early return for unknown reasons.
†† Although Ct values are not a measure of infectiousness (https://www.cdc.gov/coronavirus/2019-ncov/lab/faqs.html) a Ct cutoff of 35 was chosen by NFL based on
higher Ct values correlating with limited culturable virus using alternative RT-PCR tests (https://academic.oup.com/cid/article/73/11/e3884/6018217).
US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / February 25, 2022 / Vol. 71 / No. 8 303Morbidity and Mortality Weekly Report
NFL’s test-to-release from isolation strategy, approximately one Acknowledgments
half of fully vaccinated persons with COVID-19 had negative Monita Patel, CDC; National Football League (NFL) club
or Ct≥35 RT-PCR test results after 5 full days of isolation (i.e., infection control officers; NFL team athletic trainers, physicians, and
on day 6), and 84% by day 10. CDC advises that persons with orthopedists; NFL Players Association; NFL COVID-19 Advisory
access to tests might use an antigen test toward the end of the and Operational Team including Dawn Aponte, NFL; Michele
5-day isolation period (10), because RT-PCR tests can continue Best, University of Maryland Capital Region Health; Meghan C.
to return positive results with high Ct values intermittently Carroll, NFL; M. Anthony Casolaro, Washington Football Team;
after an initial positive result (4). Ct values are not a validated Molly Delaney, NFL; Daniel Eichner, Sports Medicine Research and
measure of infectiousness; however, the data from this study Testing Laboratory; Jacob Frank, NFL; John Lynch, Department of
indicate that persons can receive a positive test result after a Medicine, University of Washington; Jimmie Mancell, Department
of Medicine, University of Tennessee Health Science Center; Damion
5-day isolation period. It is therefore important for persons
Martins, Atlantic Sports Health, Morristown Medical Center; John
with COVID-19 to continue to wear masks correctly and Mellody, NFL; Eric Sugarman, Minnesota Vikings; IQVIA and NFL
consistently for a full 10 days after symptom onset or after an contact tracing and technical team including Megan Miraval, Ally
initial positive test result if they are asymptomatic (10). Thrasher, Sabrina Trujillo Smith, Madeline Lassiter, Emily Watson,
The findings in this report are subject to at least six limita- Kristin Archibald, Emma Bergqvist, Paul Blalock, Justin Reid, Julie
tions. First, these data are based on results from highly sensi- Griffith, Kristina Zeidler; Sequencing partners at Tempus and Yale
tive RT-PCR tests, whereas CDC advises that persons with School of Public Health.
access to rapid antigen tests might use these toward the end Corresponding author: Christina D. Mack, Christina.Mack@iqvia.com.
of the 5-day isolation period (10). Second, because of high 1IQVIA Real-World Solutions, Durham, North Carolina; 2CDC COVID-19
community incidence of COVID-19 during this period and Emergency Response Team; 3Infection Control Education for Major Sports,
limited Omicron genomic sequencing diversity, subsequent LLC, Chapel Hill, North Carolina; 4Williamson Medical Center, Franklin,
transmission postisolation release cannot be ascertained. Third, Tennessee; 5National Football League, New York, New York; 6Louisiana State
University Health Sciences Center, Baton Rouge, Louisiana; 7Eden Medical
this investigation is limited to a population of predominantly Center, Castro Valley, California; 8National Football League Players Association,
adult men in an occupational setting, who are likely healthier Washington, D.C.
than the general population, and the NFL testing program All authors have completed and submitted the International
differed from U.S. community-based testing; thus, these find- Committee of Medical Journal Editors form for disclosure of
ings might not be generalizable to other populations. Fourth, potential conflicts of interest. Christina D. Mack, Erin B. Wasserman,
Ct values from RT-PCR tests do not necessarily indicate viral and Saamir Pasha report full-time employment by IQVIA. Deverick J.
load or infectiousness in an individual person, and other fac- Anderson reports receipt of royalties for authorship from UpToDate
tors, including specimen collection and handling, can affect Ct Online, LLC and co-ownership of Infection Control Education
values (7). The use of a Ct≥35 cutoff-point for these RT-PCR for Major Sports, LLC. Patti Walton reports consulting fees from
NFL, honoraria for presentation from Ortho Clinical Diagnostics,
tests did not have Emergency Use Authorization and was not
payment as an expert witness regarding laboratory practices, support
systematically evaluated nor had either assay been evaluated
for travel to meetings from the American Society for Clinical
against the Omicron variant. Fifth, because of rapid administra- Pathology (ASCP), serving on the Board of Directors of the Clinical
tion of booster vaccine doses during the investigation period, Laboratory Management Association (2019–2021), membership on
cases could not be reported by booster dose receipt status. the ASCP Board of Governors (2019–current), and Chairmanship
Finally, symptom data were not available throughout illness; of the Tennessee Medical Laboratory Licensing Board (2019–2021).
reporting of asymptomatic status on negative test receipt was Catherine O’Neal reports consulting fees from NFL. Christopher J.
based on NFL clubs’ submission for early return permission. Hostler reports co-ownership of Infection Control Education for
In this report describing test-to-release from isolation Major Sports, LLC. Allen Sills and Emily Myers report employment
strategies in an occupational sport setting and RT-PCR test by NFL. Navdeep Singh reports receipt of consulting fees from NFL
results among fully vaccinated persons with Omicron variant and the Las Vegas Raiders. No other potential conflicts of interest
COVID-19, approximately one half had a negative result were disclosed.
or a Ct value ≥35 on or before day 6, concluding 5 days of
isolation. Although a positive RT-PCR test result does not
necessarily indicate infectiousness, these data indicate that
persons with COVID-19 should continue taking precautions,
including correct and consistent mask use, for a full 10 days
after symptom onset or after initial positive test result if they
are asymptomatic.
304 MMWR / February 25, 2022 / Vol. 71 / No. 8 US Department of Health and Human Services/Centers for Disease Control and PreventionMorbidity and Mortality Weekly Report
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US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / February 25, 2022 / Vol. 71 / No. 8 305You can also read
